Along with the growing demands of subscribers and the developing communication technologies, more and more wireless communication technologies and related networks are emerging, e.g., the 2G/3G/4G mobile communication technologies and network capable of providing wide coverage, so there are a large number of emerging scenarios in which different types of communication networks coexist, e.g., a scenario in which the 2G/3G/4G networks coexist the WLAN network.
Methods of a User Equipment (UE) performing switching in various scenarios will be introduced below in details.
1. There is a scenario in which the Universal Mobile Telecommunications System (UNITS)/Long Term Evolution (LTE) network coexists with the WLAN network.
The Evolved Packet System (EPS) is a system which supports various access technologies and mobility between them. In the multi-access scenario, the UE may be covered jointly by a number of 3rd Generation Partnership Project (3GPP) and/or non-3GPP access networks. These access networks may operate with different access technologies, may be served by different operators and also may provide accesses to different core networks. FIG. 1 illustrates the scenario in which the UMTS/LTE network coexists with the WLAN network, where there are a number of Access Points (APs) in coverage areas of base stations of the UMTS/LTE networks (a Node B in the UMTS network and an evolved Node B (eNB) in the LTE network), and coverage areas of the access points are smaller than those of the base stations,
FIG. 2 illustrates a currently supported network architecture in which the UMTS/LTE network interoperates with the WLAN network. In this architecture, the network intemperate can be completed via an S2c interface between a Packet Data Network (PDN) Gateway and the UE. At present the UNITS/LTE network interoperates with the WEAN network generally in a UE-based scheme.
2. There is a scenario in which traffic is offloaded through the WLAN network.
In the existing heterogeneous network scenario, traffic is offloaded for the UMTS/ETE network through the WLAN network, where there are generally two scenarios of seamless offloading and non-seamless offloading.
As illustrated in FIG. 3, seamless offloading refers to that there is a connection between the WLAN network and the 3GPP Core Network (CN), and traffic offloaded via the air interface still accesses the 3GPP (including UMTS/LTE) core network. As illustrated in FIG. 4, non-seamless offloading refers to that there is no connection between the WLAN network and the 3GPP Core Network (CN), and traffic offloaded via the air interface accesses the Internet directly without going through the 3GPP CN.
For offloading through the WLAN, a part of bearers of the UE may be transferred, or all the bearers of the UE may be transferred, and if a part of bearers of the UE are transferred, then the UE will be connected with both the UMTS/LTE network and the WLAN network; or if all the bearers of the UE are transferred, then the UE will be connected with only the WLAN network after they are transferred.
Further to the network scenarios and architecture above, there is an existing network selection mechanism enforced based upon the Access Network Discovery and Selection Function (ANDSF) policy. Here FIG. 5 illustrates the architecture of communication between the ANDSF and the UE, where the UE interacts with the ANDSF via an S14 interface which is an interface based upon the Internet Protocol (IP). The UE communicates with the ANDSF in both a pull mode and a push mode, where the UE pushes a request to the ANDSF on its own initiative in the former mode, and the ANDSF pushes a message on its own initiative in latter mode.
Based upon an operator policy, the ADNSF provides the UE with network discovery and selection related information including an Inter-System Mobility Policy (ISMP), Access Network Discovery Information (ANDI), and an Inter-System Routing Policy (ISRP), where:
The ISMP includes a series of operator defined rules and preferences, and this policy defines whether to allow inter-system mobility, the most appropriate type of access technology to access the Evolved Packet Core (EPC), different priorities of different access technologies, and other information. The ISMP can be preconfigured in the UE or can be transmitted when requested by the UE or can be pushed to the UE by the ANDSF under some trigger. For example the ANDSF can issue a policy with the priority of the WLAN network being higher than that of the LTE network, so that the WLAN system will be selected preferentially for an access when the UE is covered by both of the networks.
The ANDI can provide the UE with a list of available access networks, proximate to the UE, of a requested access type, and related parameters, e.g., access technologies (e.g., WLAN, Worldwide Interoperability for Microwave Access, WiMAX, etc.), radio access network identifiers, carrier frequencies, etc.
The ISRP includes some information required for inter-system routing, and for a UE with multiple radio access interfaces, e.g., a UE supporting IP Flow Mobility (IFOM) or Multi-Access PDN Connectivity (MAPCON), the information can be used to determine: a) over which of the available access networks to transmit data when a particular routing condition is satisfied; and b) when to prohibit an access to some access network for a particular IP data flow and/or a particular Access Point Name (APN).
Typically the ANDSF selects the ISMP, the ANDI and the ISRP to be provided to the UE, as required by the operator and according to a roaming protocol, and the ANDSF can provide all these three policies or can provide only a part of the policies. The ANDSF can interact with some database in the operator network, e.g., a Home Subscriber Server (HSS), etc., to retrieve information as required.
When the UE receives information about an available access network with a higher priority than that of the current access network, the UE shall perform a discovery and reselection procedure to the access network with the higher priority if this is allowed by the user. When the UE selects the access network automatically, the UE can not access the EPC through an access network marked in the ISMP as prohibited.
Apparently there is only a UE-based method but no network-based method for switching between the UMTS/LTE and WLAN networks at present. The UE-based solutions generally switch between the networks under a semi-static policy so that the UE may be switched even if the network condition is not appropriate, thus resulting in a degraded experience, and even a dropped call, of the user.